Before the product appears on the market, must accord with EMC regulation. The circuit that wants transformer and place is compositive produce EMI to the smaller conference in enclosing, because this needs to use complex and the RE with high cost restrains a technology, in order to satisfy electromagnetism compatibility (EMC) the requirement of code. According to the report, the product of 50% first EMC test ends with failing. Because lack relevant knowledge,this may be, and fail to design a technology in the inchoate application EMC of products plan phase. Want utmost ground to shorten design time and reduce project cost, undertake in the project EMC design is crucial in the begining. It is very important also to choose and be placed of package. Bring into the parts of an apparatus that accords with occupation standard choice and design to be able to rise add up to compasses sex.

 

EMC restrains technical earnestly to need better method

The traditional method photograph with transformer of use schism type is compared, mix transformer circuit is compositive to chip class package amount can reduce in enclosing, save PCB space greatly then, but may introduce taller radiate to blast off. Radiation blasts off restrain a technology to be able to make the design of PCB more complex, or need additional package, the cost that because this may offset,compositive transformer saves and space. For example, a kind of when restrain radiation to blast off in PCB level common method is to be CM electric current to form a low impedance way that from sub Duan Zhichu class carries, reduce RE level thereby. Should come true this, bypass electric capacity can be used between primary end and sub end. This bypass capacitance can be schism style electric capacity, also can be embedded interlining capacitance.

 

 

Schism style electric capacity is the simplest solution, the likelihood is to have down-lead or exterior installation package. It still has the advantage that applies to 2 PCB, but price of schism style electric capacity is high and volume is huge, can take up valuable PCB space, be in especially likelihood pile by the segregation bar of many component.

 

Another is not very good solution it is to use embedded bypass capacitance, can form this capacitance when the two faces coincide in PCB. This kind of capacitance has a few very useful character, the inductance that the reason depends on making the same score andante capacitance is extremely low, because this is effective inside bigger frequency range. It can improve emissive performance, but because need to define a layer oneself thick will acquire right electric capacity, and PCB needs 4 or more layer, so design complexity and cost are met heighten. In addition, return the kind that must carry segregation, the lowest that ensures interior overlaps the span of the layer satisfies place of relevant segregation standard to set is apart from a standard.

 

No matter be minute of vertical,still be embedded, use bypass capacitance is not ideal restrain a technology. Although it can be helped reduce radiation to blast off, in order to raise package, use complex PCB layout and raise transient state sensitivity to be cost. Ideal inhibition the technology does not need to use bypass electric capacity, because this can reduce cost and the complexity that PCB designs.

 

Product of series of IsoPower of ADI new generation

Product of series of new generation IsoPower uses the design technology of innovation, can avoid to produce a large number of radiate to blast off, go up in the 2 layer board that do not have bypass capacitance even not exceptional also. ADuM5020 and ADuM5028 are measuring contented CISPR22/EN55022B with making rich considerably kind limitation while, can cross segregation bar to provide 500mW and 330mW power respectively.

 

 

ADuM5020 is used 16 bring SOIC of crural wide system to enclose, and to ADuM5028, what can choose is the smallest enclosing is the 8 SOIC that cite a base. ADuM5020/ADuM5028 offers 3V and 5V option of two kinds of power source, and 3kV Rms rated segregation.

 

Blast off to reduce radiation, ADuM5020/ADuM5028 has outstanding coil symmetry and coil drive circuit, conduce to the CM electricity that will carry segregation bar transmitting the smallest change. Enlarge frequency technology also is used to reduce some the noise chroma of specific frequency, diffuse radiation emissive energy more extensive frequency paragraph. In ferrite of sub end use low magnetism bead can reduce radiation to blast off further. During RE combines compasses test, these technologies can improve peak value and exact peak value to measure a level.

 

 

(origin: Yadenuo semiconductor)